Superagonism at G protein-coupled receptors and beyond.

Ligands targeting GPCRs can be categorized according to their intrinsic efficacy to trigger a specific, receptor-mediated response. A ligand endowed with the same level of efficacy as the endogenous agonist can be classified as a full agonist, whereas a compound that displays greater efficacy, that is, higher receptor signalling output than the endogenous agonist, can be called a superagonist. Subsequent to GPCR activation, an intracellular signalling cascade is set in motion, which may generate substantial amplification of the signal. This may obscure superagonism in pharmacological assays and, therefore, the definition of superagonism necessitates a combination of operational approaches, reduction of spare receptors or estimation of receptor activation close to the receptor level to quantify relative agonist efficacies in a particular system. The first part of this review will compare GPCR superagonism with superagonism in the field of immunology, where this term is well established. In the second part, known GPCR superagonists will be reviewed. Then, the experimental and analytical challenges in the deconvolution of GPCR superagonism will be addressed. Finally, the potential benefit of superagonism is discussed. The molecular mechanisms behind GPCR superagonism are not completely understood. However, crystallography shows that agonist binding alone is not sufficient for a fully active receptor state and that binding of the G protein is at least equally important. Accordingly, the emerging number of reported superagonists implies that ligand-induced receptor conformations more active than the ones stabilized by the endogenous agonist are indeed feasible. Superagonists may have therapeutic potential when receptor function is impaired or to induce negative feedback mechanisms. Linked Articles This article is part of a themed section on Molecular Pharmacology of G Protein-Coupled Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.20/issuetoc.

Agonists with supraphysiological efficacy at the muscarinic M2 ACh receptor.

BACKGROUND AND PURPOSE: Artificial agonists may have higher efficacy for receptor activation than the physiological agonist. Until now, such 'superagonism' has rarely been reported for GPCRs. Iperoxo is an extremely potent muscarinic receptor agonist. We hypothesized that iperoxo is a 'superagonist'. EXPERIMENTAL APPROACH: Signalling of iperoxo and newly synthesized structural analogues was compared with that of ACh at label-free M2 muscarinic receptors applying whole cell dynamic mass redistribution, measurement of G-protein activation, evaluation of cell surface agonist binding and computation of operational efficacies. KEY RESULTS: In CHO-hM2 cells, iperoxo significantly exceeds ACh in Gi /Gs signalling competence. In the orthosteric loss-of-function mutant M2 -Y104(3.33) A, the maximum effect of iperoxo is hardly compromised in contrast to ACh. 'Superagonism' is preserved in the physiological cellular context of MRC-5 human lung fibroblasts. Structure-signalling relationships including iperoxo derivatives with either modified positively charged head group or altered tail suggest that 'superagonism' of iperoxo is mechanistically based on parallel activation of the receptor protein via two orthosteric interaction points. CONCLUSION AND IMPLICATIONS: Supraphysiological agonist efficacy at muscarinic M2 ACh receptors is demonstrated for the first time. In addition, a possible underlying molecular mechanism of GPCR 'superagonism' is provided. We suggest that iperoxo-like orthosteric GPCR activation is a new avenue towards a novel class of receptor activators.

[Psammoma bodies in cytological vaginal smears in metastatic ovarian carcinoma]. / Psammomkörperchen im zytologischen Vaginalabstrich bei metastasierendem Ovarialkarzinom.

The case of a 37-year old patient with ovarian cancer stage FIGO IV and vaginal metastasis is reported. The vaginal smear showed psammoma bodies, which are rarely found. The value of the diagnosis "psammoma bodies" is discussed, via a review of the literature.

[The value of colposcopy and portio biopsy in preventive examination]. / Zum Stellenwert der Kolposkopie und der Portiobiopsie bei der Vorsorgeuntersuchung.

133 patients attending the colposcopy-laser outpatient consultations were examined simultaneously by cytology, colposcopy and punch biopsy. A cone biopsy was taken 25 patients and one patient was hysterectomised later. A comparison between cytology and histology revealed 17.1% false negative smear results. Cytology and histology showed the same result in 84.6%. The highest percentage of high-grade dysplasia was found in colposcopy with signs of punctation and/or mosaicism. A similar diagnosis was achieved in 92.3% of cases comparing punch with cone biopsy. Simultaneous use of cytology, colposcopy and punch biopsy enables reliable diagnosis and follow-up of dysplastic lesions of the cervix. Besides, one can use punch biopsy as basic histology for local destructive manoeuvres such as laser vaporisation.

[Suspected abortion: morphologic aspects--value of histological examination of curettage specimen in suspected abortion and extra-uterine pregnancy]. / Abortverdacht: Morphologische Aspekte--Aussagefähigkeit der histologischen Untersuchung des Abradates bei Abort- und EUG-Verdacht.

Curettage specimens of 104 patients with clinically suspected abortion and unknown localization have been examined histologically. 50 patients with defined ectopic pregnancy, 51 patients with proved abortion and 50 patients with legal abortion had been used to compare with. In two cases syncytial cells could be proved histologically and by this an abortion could be verified. We could see decidually transformed endometrium in all cases with uncertain or certain formerly intrauterine localization of pregnancy. Opposite to this in ectopic pregnancy we could observe this only in 54 per cent. Summarizing our results in abortions as well as in ectopic pregnancies similar histologic findings could be seen.

[Attitude of patients to chorionic villi biopsy: motivation for the decision and perception]. / Einstellung von Patientinnen zur Chorionzottenbiopsie: Entscheidungsmotivation und Empfinden.

56 patients with CVS were asked with a standardized questionnaire why they decided to undergo that surgical procedure and how they felt about it. 52 patients said, that their main motivation for CVS was the early diagnosis of a healthy baby. The low health risk of an early performed abruption in case of fetal abnormalities played a secondary role. Concerning the severity of that surgical procedure 44 patients thought, that it was harmless or tolerable and no woman had the feeling that CVS is a fearful intervention. 76% said, that CVS was not painful or only a little bit, 2 patients had the feeling of a painful surgical procedure. The most disagreeable moment during CVS was the hooking of the cervix. There were different opinions comparing CVS stress to amniocentesis stress in patients with a preceding amniocentesis.

[Cancer register problems--modified reporting law model for the improvement of data protection]. / Zur Krebsregisterfrage--modifiziertes Melderechtsmodell zur Verbesserung des Datenschutzes.

The author suggests creating a "Reporting Law Model with Peripheral Part Anonymisation" that preserves the advantages of the reporting law model which are internationally recognised in respect of reliability of registration, on the one hand, while on the other hand the general and individual requirements of sufficient protection of sensitive data are also taken care of. This is achieved by separating the personal data from the factual data at the reporting office level. These data are transmitted separately to the registration offices and their confidential files. It is nevertheless possible to detect any double or multiple reporting and to perform fault finding in respect of personal data. It is also possible to add further data to any patient's case history. This cancer registration model can always cope with the required descriptive and analytical epidemiological tasks that are expected of it. It can be arranged to cover a wide area in a continuous manner without loss of time and without considerable expenditure. Documentation work to be performed by the reporting offices is minimised.

[Chlamydia trachomatis--studies on the reliability of its detection in Papanicolaou preparations]. / Chlamydia trachomatis--Untersuchungen zur Wertigkeit des Nachweises im Papanicolaou-Präparat.

In a matched group of 104 chlamydia culture-positive and 104 culture-negative women, the correlation between simultaneous cultures and cytological findings in the Papanicolaou smear was studied. Cellular changes in metaplastic cells that are described in the literature as being specific for Chlamydia trachomatis, were not associated with genital chlamydial infection. In particular the reported high sensitivity of intracytoplasmatic inclusion bodies could not be confirmed. Likewise, even severe inflammatory changes and a high concentration of lymphocytes were also no reliable diagnostic indicator. The authors conclude that the Papanicolaou smear is not useful as a routine screening method for genital chlamydial infection.

[Chlamydia trachomatis--cytologic findings in infections of the uterine cervix]. / Chlamydia trachomatis--zytologische Befunde bei Infektion der Cervix uteri.

Cytologic, colposcopic, histologic and bacteriologic examination was performed in 229 patients because of previous abnormal cervical cytology. Chlamydia trachomatis was found in a significantly greater proportion as well in 70 women with spontaneous recurrence to normal (17.1%) as in 85 women with dysplasia (17.6%). In comparison, chlamydial infection is found in 4.1% of cytologically normal women. In the 2 to 22 months follow-up Chlamydia trachomatis was seen in 19.6% of 92 women with recurrence to normal cytologic pattern, however, in 10.8% of 65 patients with persistence or progression (p less than 0.025, t-test).

Amniotic fluid cells in the second trimester of pregnancy.

The cell types of amniotic fluid in the second trimester of normal pregnancy are described and compared with the findings in the literature. Two hundred cell samples obtained by amniocentesis in pregnancies without known fetal neural tube or skin defects were studied. Anucleated and nucleated squamous epithelial cells of superficial and intermediate layers were found, as were macroforms of superficial cells. Parabasal cells were infrequent. Parabasallike cells were of amniotic origin. Other amniotic cell types, such as "balloon," or "goblet," cells, umbilical cord cells and hyperchromatic placental amniotic cells, were observed. Urothelial cells and nonepithelial cells, such as histiocytes and macrophages, were found. In several cases, "minicells" were seen; their different sites of origin are discussed.

[Problems of current diagnosis of neoplasms in women]. / Probleme der heutigen Krebsfrüherkennung bei der Frau.

The value of early cancer detection in women is limited by the screening methods and their minor reliability in "mass-screening". The effect of detection programs is difficult to demonstrate. The interest in cancer detection is low, especially in elderly high risk patients. A more suitable application of screening tests with widespread indication of further methods together with exact demonstration could be the basis for better results in early cancer detection programs in women.

[Results of cancer screening in women (author's transl)]. / Ergebnisse der Krebsfrüherkennung bei der Frau. Eine Auswertung in Nord- und Südwürttemberg-Hohenzollern

The results of cancer screening in women were evaluated from 1,1 million investigations during the third quarter of 1971 to the second quarter of 1974. Positive cytological results of the uterine cervix were found in 0,39% on first investigation and in 0,38% on repeat investigations. Positive results in the breast amounted only to a quarter (0,1%) of the frequency of positive cytological results despite the fact that breast cancer occurs more frequently than cervical carcinoma. Only 0,03% positive findings were obtained by digital rectal palpation. The low incidence of the diseases sought for and the partly low sensitivity of the screening methods are responsible for the small numbers of positive findings in early detection investigations and are an indication of the effort involved. Participation of the population in investigations for early detection of cancer is unsatisfactory especially in older age groups with an increased risk.

[Are more girls than boys born in breech presentation compared with head presentation?]. / Werden bei der Beckenendlage mehr Mädchen als Knaben geboren im Vergleich zur Kopflage

In breech presentations a little more girls are born than boys, among head presentations there is a slight excess of boys. Among the factors favoring pelvic presentation birth weight has, according to present investigations, a decisive influence on the different sex relationship in the two presentations. Boys are little more common than girls in head presentation in the higher weight groups, in breech presentation in the upper and lower weight groups, while girls predominate in the middle weight groups. The absolute size of the middle weight groups in breech presentation causes the small excess of girls. A possible link with the slightly higher mortality of boys during the first year and its higher incidence in very high and very low weight groups are discussed as well as the dependence of the production of breech presentation on weight and mobility of the fetus.

[The diagnosis of corpus carcinoma (Differentialdiagnostic importance of history- and clinical criteria in post-menopausal hemorrhage) (author's transl)]. / Zur Diagnose des Korpuskarzinoms (Differentialdiagnostische Bedeutung anamnestischer und klinischer Kriterien bei der Postmenopausenblutung)

Among 1554 patients with post-memopausal hemorrhage over 7 years one half were due to benign causes, the other in almost equal parts to carcinoma of the fundus or cervix. Ca of the fundus is more likely when post-menopausal bleeding occurs at a relatively old age, a late menopause and a long interval between menopause and post-menopausal bleeding. Nulliparae more often have Ca of the corpus than in the cervix or have benign changes. The trias known for the corpus Ca: adiposity, diabetes and hypertension is confirmed. An enlargement or softening of the uterus and myomatous changes also indicate Ca. Anatomical and clinical criteria permit not only a detailed assessment of post-menopausal bleeding but also a definition of cases at risk before bleeding occurs and give an indication for detailed investigations.